Another Newbie Question

[Shadowstalker]

After loading my very first rounds (.40S&W), shooting the test batches, and running a batch of the load that gave me the best results for grouping and recoil; I going to "move up” to rifle rounds but I have a few questions that I’m certain have been asked before, so I apologize in advance for the Newbie Questions.
7mm Rem Mag: I have 2 of these rifles (Browning BAR and a new Savage bolt), and the majority of the brass came from the Savage when I was trying to find a round that the rifle liked. The majority of these rounds I load will be shot from the Savage as it is a much more accurate rifle than the BAR, but I will also be looking for a load that the BAR likes. I’ve cleaned, deprimed and full length sized the brass. These will be primarily hunting rounds in a variety of climates
- The load from Barnes call out for the Brass to be 2.490, but my once fired brass has lengths of 2.512 +/-.002 (these came from the BAR), and 2.500 +/-.003. Do I need to worry about case trimming if I shoot them from the same rifle, or if I didn’t case trim can I shoot the different brass out of both rifles (of which I’m assuming would give me mixed accuracy results). I guess I’m really also asking about acceptable variations in tolerances, because it’s a difference of only 1/100th and 2/100th of an inch in variations
- I also have new brass that is at 2.490 +/-.002 that I’ll be loading as well, will I get different accuracy results from using this brass because the bullet will be seated at a different place to keep the OAL the same?
- Barnes calls for an OAL of 3.240 but the factory Federal Premium in the same bullet have an OAL of 3.225. Why would Barnes call out for that and a major ammo manufacturer load it differently. At the shorter OAL the rings in the bullet are not exposed
- Barnes also suggests for best accuracy to seat the bullet so that it is .050 from the lands. How can I measure that and what if that is in conflict of their OAL

.338 Win Mag: This is a little easier because I have about 150 pieces of once fired brass that have been fired out of that rifle only and will only be fired from this rifle, but essentially the same questions as above

Thanks for passing on your knowledge

[Shoney]

The minimum case length (trim length) of the 7Mag is 2.490". When the brass is at or exceeds 2.500" it needs to be trimmed.

Federal uses the shorter OAL to make sure it fits in a wide variety of magazines. The magazine lengthis usually the limiting factor on the OAL you can use to feed from the magazine. The longer AOL's which are at/about 0.050 off the lands, usually do not fit the magazine and have to be hand chambered, one at a time.

If you want to know why??? you load off the lands, read my second post in this thread

http://thefiringline.com/forums/showthread.php?t=358993

[briandg]

do not interchange the rounds between your BAR and your bolt. Generally, with a bolt, you can neck size only, but your BAR will require full length sizing, and it will stretch your brass worse than a bolt will. In some expert opinions, a semiauto high powered rifle shouldn't have brass reloaded more than 3 or 4 times anyway. My suggestion would really be stay with factory for your BAR, or at least, buy a different brand of brass for it so that you will not exchange them by accident.

Read your manual for some advice on full length, partial, or neck only sizing, and remember, the bar will require full length every time.

Don't worry about measurements of brass or OAL that vary by 1 or 2 1/100" These are all pretty nominal, and small variations like that will have very little effect on the overall accuracy of a round. Different bullets are built differently, and the differing OAL is to be expected from one maker to the next. As long as it functions, what matters is actually distance to lands, not OAL.

Your barnes bullet suggests .05 of what is called "free bore" before contact with the bullet and the lands. Seriously, very few reloaders can even measure that bit of information, becasue it takes special equipment to do so with that precision. Use their suggested oal, and forget that issue.

All of the little tiny details measured by micrometers and so forth will not make a noticeable difference in your accuracy unless you are a competitive bench rest shooter.

With your rifles, I suggest that you use only 1 brand of brass, or keep them segregated by make. If that's just not possible, due to a whole pile of mixed makers and dozens of boxes, such as range pickups, at least weigh them out, and segregate them by weight, if there are differences of 3 grains or more. I'm talking about differences of several grains, not 1/100 grain.

Someone else needs to step in on the brass weight issue,though, I've not got the experience to really argue that point. I do know that every maker will have differences between design, and each shell can have variations, and when your combustion chamber is irregular in size, your accuracy can vary. Even flash holes can have a tiny effect on overall accuracy.

[SKULLANDCROSSBONES65]

G'day and welcome to TFL.

- Barnes calls for an OAL of 3.240....Why would Barnes call out for that and a major ammo manufacturer load it differently.

You will find this is the maximum OAL. The major ammo manufacturer is less than maximum.

[zippy13]

You seem to have done your homework. Happy to hear your pistol loads have been successful. You'll soon have your loads dialed in and wonder: Why anyone would want to shoot factory loads when they can have hand load accuracy, and savings, with so little effort?

On to the bottle neck rounds… Let's start with case length: With your .40 S&W, you're headspacing at the case mouth as contrasted to your magnum rifles spacing at the belt. Theoretically the case length is more critical with the .40 S&W over the rifle. That doesn't mean you can over look you rifle's case lengths. With the higher working pressures of the belted magnums, the brass has a greater tendency to flow than with pistol ammo. You don't want your rifle cases so long that the start encroaching into the area of the forcing cone.

My data show the 7mm Rem Mag case to have a max length of 2.500-inch. So without slugging the chambers, of both of your 7mm mags, to determine their actual dimensions, to be on the conservatively within specs, your 2.500 +.003 and your 2.512s are candidates for the case trimmer. The Barns spec for trimming them to 2.490 is the standard "trim to" length. Your observation is correct, there's only 1/100-inch between the max case length and the trim-to length. Do you have a standard case length gauge?

Surprise, surprise! Your .338 Win Mag has the same case length specs as the 7mm Rem Mag -- the same gauge will do both cases. This may make you case prep work much simpler.

What's up with loaded cartridge overall length? The main in thing the specs are looking for is that standard cartridges aren't so long that they don't fit in standard magazines and that the bullets not be jammed by the rifling when loading. This doesn't help accuracy and could conceivably cause the bullet to move and compress the powder.

Holding the bullet .050-inch off of the lands sounds good in the bullet maker's specs; but, it may not be that easy. You can check the archives, some reloaders run into problems when trying to determine "jump" distance. Since it probably won't be nearly the same between your two 7mm mag's. It's is another reason to keep your loads segregated by gun.

May I suggest you start with the easier cases, the .338 Win Mags. Because they are a little bigger, IMHO, they're easier to manipulate. And, you'll be avoiding the complications of the 2 different rifles.

Good luck with your rifle reloading, hope you are as successful with them as you are with .40s.

[Shadowstalker]

Thanks for the info so far. I will case trim anything longer than 2.500, and from now on keep the brass separate.
Can you tell me if my next assumptions are correct? The brass from the BAR will have been shaped differently than from the bolt; so I'm assuming I will get different accuracy results from the BAR brass. I have already full length sized the brass that came out of both rifles? I might be able to look through and pick out some of the brass from the BAR as it leaves a telltale mark. Also, will leaving a portion of the ring exposed affect the accuracy.
Or am I worrying to much about the smallest of small details?

[Shoney]

Brass for each weapon should be kept separate, and accuracy loads should be established for each weapon. The BAR will require a full length resize every time in order to enable positive feed without hang-ups.

As with all bolt action rifles, it is better for accuracy, that once the brass has been fireformed to the chamber, it should be either neck sized or adjust the sizing die so it just bumps the shoulder. in effect, you are then headspacing off the shoulder.

Since your barss has already been FL sized, it is not critical that you have the brass matched to the weapon. However, after the fireforming is completed for the bolt rifle, either neck size or bump.

Also, will leaving a portion of the ring exposed affect the accuracy.

Could you explain more what you mean by ring.

[Unclenick]

3.290” is the SAAMI maximum COL for the 7m Rem Mag. That tells you what is compatible with SAAMI compliant magazines made for that round. Shorter COL recommendations are usually specific to the bullets involved, especially when they have a cannelure that sets the level of the case mouth if you intend to apply a crimp? There is no SAAMI minimum COL because SAAMI doesn’t know how short a bullet you will try to load? A bullet with a short ogive profile, such as a round nose, even though long, may not be able to be seated out to the SAAMI maximum without bumping into the throat of the bore when you try to chamber it. The SAAMI maximum only determines that a cartridge of that length will fit the magazine, and not that it will fit the chamber.

Case trim for the 7 mm Rem Mag is specified as 7.500” -0.020”. That means 7.500 is its maximum and 7.480” is its minimum. Most trimming specs aim for the middle of the range so you don’t run over or under the limits. But if you have a precise trimmer, you can aim for the minimum so you don’t have to trim as frequently. Also, for cases that don’t have extremely short necks, the minimum is not critical if you are not going to crimp the bullets. Many match shooters trim the .308 about -0.030” to -0.040” below maximum just so they wouldn’t have to trim a case again before they retired it. They do keep the same lot together and see that it experiences the same load history, for consistency, but they don’t use a crimp. Observing the minimum is important if you want the case mouth to be certain to be able to reach the crimp contour in all seating dies.

The maximum dimension is another story. It is a safety issue. If you let a case get too long it can jam into the end of the chamber where the freebore starts. This increases the pressure required to open the case mouth to release the bullet. That pressure rise can be dangerous. It does not require that the case be long enough to touch the end of the chamber to be dangerous, but just that the case stretches that far under pressure while the round is firing. As a result, most chamber reamers have an extra 0.020” or so beyond the SAAMI maximum case length to allow for that stretching plus some leeway for shooter error.

Note that the above hazard arises after the cartridge has been loaded into the gun. That means it is after the case has been resized. Sizing will squirt some brass forward into the die as it squeezes the sides narrower, thus lengthening the brass even after is goes deeply enough into the die to set the shoulder back. So, it is crucial that you check and correct case length after sizing. This is a nuisance on a progressive press. For that reason I think the RCBS X-die, which limits case growth with an internal stop, is the best thing to use on a progressive press. You have to trim the brass once to its SAAMI minimum when it is new, but afterward don’t need to worry about it again if you use this type of die. It will limit subsequent growth to within SAAMI maximum.

The BAR, as noted, will likely stretch brass more. That shortens its life, so you will need to replace it more often to avoid head separations. It is also possible to pull brass long enough that it can't be resized for a tighter chamber properly. It never returns 100% to original size without special undersized dies or by roll sizing as many brass processors use. However, as long as you associate a set of brass with one chamber, starting new, a conventional die will always reduce it far enough to return to that same chamber as long as the rim has not been bent out.

[Shadowstalker]

Gentlemen.
Thank You so much for all the info, this forum is great for beginners

[ace_31]

First post. just wanted to say thanks for all the great info from you gents. Good question and good answers!